Sweet or salty? Historically among Eastern European Jews, how they liked their gefilte fish depended on where they lived. This divide created a strictly Jewish geography known as "the gefilte fish line." Claire Eggers/NPR hide caption

itoggle caption Claire Eggers/NPR

Researchers raised two groups of walking, air-breathing Polypterus senegalus — one on land and one on the water. They discovered that each group was able to adapt to be best suited to its environment. A. Morin, E.M. Standen, T.Y. Du, H. Larsson/McGill University hide caption

itoggle caption A. Morin, E.M. Standen, T.Y. Du, H. Larsson/McGill University

Asian carp, battered and fried. As the fish makes its unwelcome way up the Mississippi River, chefs are trying to get people to eat to beat it back. Louisiana Sea Grant/Flickr hide caption

itoggle caption Louisiana Sea Grant/Flickr

These undated photos provided by the Colorado Division of Wildlife show the endangered greenback cutthroat trout and the Colorado River cutthroat trout. Federal and state biologists have stocked the wrong fish for more than two decades. AP hide caption

itoggle caption AP

Using dipnets --€” which have nets up to 5 feet in diameter at the end --€” isn't easy, and the river can get pretty crowded. Robert Carter, a novice dipnetter, holds up the first fish he caught after a day on the Kenai River. Annie Feidt/Alaska Public Media hide caption

itoggle caption Annie Feidt/Alaska Public Media

Yellowfin tuna; Chinook salmon; lingcod; Pacific halibut. Chang/iStockphoto; Debbi Smirnoff/iStockphoto; via TeachAGirlToFish; Andrea Pokrzywinski/Flickr hide caption

itoggle caption Chang/iStockphoto; Debbi Smirnoff/iStockphoto; via TeachAGirlToFish; Andrea Pokrzywinski/Flickr

The FDA is recommending that pregnant women eat 8 to 12 ounces per week of fish such as salmon, canned light tuna, tilapia or cod. Iakov Filimonov/iStockphoto.com hide caption

itoggle caption Iakov Filimonov/iStockphoto.com

Carp are collected at a breeding farm near the Belarus village of Ozerny in November 2013. Researchers say there's a lot the aquaculture industry can do to be more efficient. Viktor Drachev/AFP/Getty Images hide caption

itoggle caption Viktor Drachev/AFP/Getty Images

A tuna fishing boat drags a cage of nets on the Mediterranean sea in 2010. (The Mediterranean is not considered to be part of the "high seas.") Andreas Solaro/AFP/Getty Images hide caption

itoggle caption Andreas Solaro/AFP/Getty Images

A marlin caught as bycatch by the California drift gillnet fishery. The conservation group Oceana called the fishery one of the "dirtiest" in the U.S. because of its high rate of discarded fish and other marine animals. Courtesy of NOAA hide caption

itoggle caption Courtesy of NOAA

A fish that knows the way to go: the Chinook salmon, which appears to use the Earth's magnetic field to navigate ocean waters and rivers. Jeff T. Green/Getty Images hide caption

itoggle caption Jeff T. Green/Getty Images

How to make dead fish look attractive? That's the challenge New York-based duo Shimon and Tammar Rothstein faced when they were hired to do the photography for famed French chef Eric Ripert's book On the Line. Photos by Shimon and Tammar, Courtesy of Shimon and Tammar hide caption

itoggle caption Photos by Shimon and Tammar, Courtesy of Shimon and Tammar